Sent sms using api

i purchased sms gateway and i have an api of that getway but when i sending a sms to mobile all code working fine but not getting sms please solve my issue its urgent my code is

public void send()

{

String sURL;

System.IO.StreamReader objReader;

sURL = @"http://nimbusit.co.in/api/swsendSingle.asp?username=##########&password=##########&sender=SenderID&sendto=##########&message=hello";

System.Net.WebRequest wrGETURL;

wrGETURL = System.Net.WebRequest.Create(sURL);

try

{

System.IO.Stream objStream;

objStream = wrGETURL.GetResponse().GetResponseStream();

objReader = new System.IO.StreamReader(objStream);

objReader.Close();

}

catch (Exception ex)

{

ex.ToString();

}

protected void BtnSent_Click(object sender, EventArgs e)

{

send();

ScriptManager.RegisterStartupScript(this, this.GetType(), "popup", "alert('sms sent successfully...');", true);

}